Blood gases are by far the most frequently monitored chemical parameters. Arterial oxygen (PaO2) is needed to assess the efficiency of O2 exchange. Arterial carbon dioxide (PaCO2) is needed to assess efficiency of ventilation and is most useful for ventilator management. However, because arterial blood sampling is not practical in many clinical situations, there is a need for noninvasive blood gas monitoring which does not rely on laboratory measurements for references. This proposal introduces a new concept for a noninvasive arterial blood monitor which applies metabolic correction applied to transcutaneous carbon dioxide measurements. The correction is derived from cutaneous oxygen metabolism data obtained from the differences of arterial and transcutaneous oxygen measurements at the site of the cutaneous carbon dioxide sensor. The new principle incorporates automatic calibration of cutaneous measurements and a sufficiently low skin contact temperature, to eliminate the need for periodic relocation of the measuring device. The arterial oxygen measurement utilizes a new concept of pressure enhancement applied to pulse oximetry. Because arterial blood sampling is not practical in many clinical situations, there is a need for noninvasive blood gas monitoring which does not rely on laboratory measurements for references. The overall goal of the project is to develop a monitor which can provide accurate and reliable blood gas data, noninvasively, without need for additional laboratory measurements for reference. [unreadable] [unreadable] [unreadable]